Strapping machines are in widespread use for securing straps around loads. There are two principle types of strappers. One type is a manually operated hand tool that can be used, for example, around a job site. Another type of strapper is a stationary arrangement in which the strapper is fabricated as part of an overall apparatus. In such a strapper, the strapping head and drive mechanisms are typically mounted within a frame. A chute is likewise mounted to the frame, through which the strapping material is fed.
In a typical, stationary strapper, the strapping head is mounted at about a work surface, and the chute is positioned above the work surface and above the strapping head. Strap material is fed to the strapping head by a set of feed and take-up wheels. The strapping material is fed, by the feed wheels past the strapping head, around the chute and back to the strapping head. The free end of the strapping material is then grasped, such as by a first part of a gripping arrangement. The strap is then retracted by the take-up wheels and tensioned around the load. The tensioned strap is then gripped by a second part of the gripping arrangement. A cutter in the strapping head then cuts the tensioned strap (from the source or supply) and the strapping head forms a seal in the strapping material, sealing the strapping material to itself around the bundled load.
Strapping operations are typically secondary operations in that these operations are used for bundling or securing individual items into a single, large load. The straps themselves are not of commercial concern to the end user; rather, it is the bundled items that are of concern. As such, it is important to be able to strap and move the items quickly and in a cost effective manner.
To this end, improvements have been made to strapping machines. One such improvement includes an auto re-feed arrangement, such as that disclosed in Bell, et al., U.S. Pat. No. 5,640,899, commonly assigned herewith. In such an arrangement, in the event of a misfeed of strapping material, the misfed strap is cut and ejected from the machine. Fresh strapping material is then automatically re-fed by the feed wheels through the strapping head and around the load. It has been found that such an arrangement saves considerable time and labor vis-à-vis removing the misted or snapped strap and refeeding strap material into the strapper.
One drawback to the known re-feed arrangements is that they require separate feed and take-up wheels. That is, a pair of wheels (generally one driven and one idle) is required to feed the strapping material through the strapping head and the chute. A second, separate set of wheels (again, one driven and one idle) is required to take-up or retract the strap in order to tension the strap around the load. While these automatic re-feed arrangements have been found to save considerable time and labor, the requisite two pairs of wheels introduce additional maintenance concerns as well as timing arrangements with respect to the overall operation of the machine.
It has also been found that typically, these stationary types of strappers are designed and constructed such that the feed and take-up mechanism is located near to the strapping head. Because of the proximity of the feed and take-up arrangement to the strapping head, two sets of feed and take-up wheels are required in order to meet the overall operating requirements, given the physical constraints of the equipment.
Present designs of stationary strappers, which include a closely located feed and take-up mechanism to the strapping head, also include guide paths to, from and between components that are all fixedly mounted to the machine. In the event of maintenance or repair, the machine must be taken out of service for the duration of that work. In addition, skilled technicians are generally required to tend to the machine during the entirety of the maintenance or repair procedure.
It has further been observed that the guides of known strappers, that is those portions of the strapper along which the strap material is guided while it is fed around the strap path tend to clog with debris from the strapping material. This debris can either be residue from the plastic strapping material itself, or debris that is carried by the strapping material into the machine. Typically, these guides have very small clearances between the guides themselves and between the guides and the active (driven or idle, rotating) machine components. As a result, it is necessary, at times, to shut down the machine, open the guide paths and clear these guide paths of debris. Known machines typically require disassembly of those portions of the machine which, again, requires significant labor and time. In addition, strappers are known to occasionally jam, in which strap material may get caught at about the active machine components or between the active and stationary machine components. In order to clear or remove these jams, again, the guide paths require disassembly necessitating time and labor.
Another concern with known strapping machines is that at times, the strap is not aligned with itself prior to forming the seal or xe2x80x9cweldxe2x80x9d. In order to achieve maximum tension strength in the strap joint the strap should be fully aligned with an adjacent layer of strap prior to welding. This maximizes the area over which the weld is performed. Known strappers rely upon an alignment of stationary strap guides or paths in order to properly position the strap material in this aligned, adjacent arrangement. However, at times, the strap shifts as it is aligned or prior to welding, resulting in misaligned straps and less than optimal joint strength.
Accordingly, there exists a need for a strapping machine that utilizes modular components, specifically for the drive and sealing functions. Desirably, such modular components are readily removed and installed in machines to minimize the xe2x80x9cdown timexe2x80x9d of such machines. Most desirably, such modular components are readily installed and removed, with minimal or no tools. Further, a need exists for a strapper that minimizes clogging and provides easy access to the guide areas. Again, most desirably, access is provided to these areas with minimal or no tools. Still more desirably, the guide pathway and covering therefor are formed as integral units further minimizing disassembly to clear these paths. In such a strapper, an auto re-feed arrangement is desirable without the use of separate feed and take-up wheels. A need further exist for a strapper in which strap alignment, prior to welding, is actively provided.
A strapping machine positioning a strapping material around an associated load and seals the strapping material to itself around the load. The strapping machine includes a frame, a chute defining a strap path mounted to the frame, a modular feed assembly mounted to the frame, a guide mounted to the frame adjacent the feed assembly, and a modular strapping head mounted to the frame independent of the feed assembly and the guide.
The feed assembly is configured to feed the strapping material from a source to the guide. The guide is mounted to the frame independent of the feed assembly and the strapping head. The guide is configured to receive the strapping material from the feed assembly and to provide a path for the strapping material toward the strapping head.
The strapping head includes a body and provides a conveyance path for the strapping material to the chute. In one embodiment, the strapping head defines a first conveyance path for the strapping material from the guide to the chute, and a second conveyance path to receive a free end of the strapping material to seal the strapping material to itself.
Preferably, the strapping head includes an anvil movably mounted to the body and forming a part of the second conveyance path. The anvil is movable between a first conveying position in which the anvil is pivoted away from the body to enlarge the second conveyance path and a second sealing position in which the anvil is pivoted toward the body to narrow the second conveyance path.
The anvil can be pivotally movable toward and away from the body. Preferably, the anvil is biased toward the body. In this arrangement, strapping head includes a side plate pivotally mounted to the body. The anvil is fixedly mounted to the side plate. The strapping head can include a cam for moving the anvil between the first conveying position and the second sealing position. The cam cooperates with the side plate to pivot the anvil.
The present strapping machine further contemplates an embodiment in which a controller controls the operation of the strapping machine. The controller is operably connected to the feed assembly.
A sensor is disposed to sense the presence and absence of strapping material at the strapping head. The sensor includes first and second movable elements, preferably paddles, that cooperate with one another. The paddles are movable between a first position in which the sensor senses the presence of strapping material and a second position in which the sensor senses the absence of strapping material. The sensor is operably connected to the controller and when the sensor senses the absence of strapping material at the strapping head, a control signal is generated to initiate operation of the feed assembly in a refeed mode.
In a current embodiment, the sensor is mounted to the strapping head at about a strap exit path of the strapping material from the strapping head. Preferably, the paddles pivot about a common pivot pin. The strapping material engages the first paddle to pivot the paddles between the first and second positions.
The sensor can include a proximity sensor cooperating with the first and second paddles. The second paddle is positioned between the proximity sensor and the first paddle being. The first paddle is biased toward the proximity sensor and the second paddle is biased away from the first paddle. First and second biasing elements bias the first paddle toward the proximity sensor and the second paddle away from the first paddle, respectively.
A hinge stop limits travel of the first and second paddles away from one another. The second paddle operably contacts the proximity sensor during the feed mode and the take-up mode, and the second paddle is operably separated from the proximity sensor during a refeed mode.
A preferred strapping head includes a second conveyance path to receive a free end of the strapping material to seal the strapping material to itself. The second conveyance path is defined by a plurality of surfaces within the body. The surfaces define a substantially constant width path through the second conveyance path.
An entryway precedes the second conveyance path. The entryway has a larger path width than the conveyance path width. A gripper is disposed at a terminal end of the conveyance path.
The strapping machine further contemplates an easy access transfer guide mounted to the frame between the feed assembly and the strapping head. The transfer guide includes a fixed portion and a cover portion. The fixed portion is fixedly mounted to the frame independent of the feed assembly and the strapping head. The transfer guide is configured to receive the strapping material from the feed assembly and to provide a path for the strapping material toward the strapping head. The cover portion overlies the fixed portion along a plane that is substantially parallel to the a plane defined by a longitudinal axis and a width of the strapping material.
In a preferred arrangement, the cover portion is pivotally mounted to the fixed portion by hinges and is retained in place covering the fixed portion by at least one, and preferably multiple mechanical fasteners. Most preferably, the mechanical fasteners are knurled to permit tool-less loosening. In a current embodiment, fasteners include a hinge-supported portion, so that when the fasteners are loosened from the cover portion (e.g., pivoted away from the cover portion) the hinge-supported portions retain the fasteners mounted to the fixed portion.
The strapping machine can further include an easy access feed guide for covering at least a portion of the feed assembly. The feed guide includes a cover for covering at least a portion of the feed assembly and an arcuate guide wall transverse to the cover. The guide portion is generally parallel to the strapping material as is traverses through the guide. The guide wall is spaced from a periphery of one of the feed wheels at about an entry of the strapping material into the feed guide and converges toward a periphery of the one of the feed wheels as the guide wall approaches the nip of the feed wheels.
The cover portion is removably mounted to the fixed portion by mechanical fasteners. Preferably, the fasteners are knurled to permit tool-less loosening. Most preferably, hinge-supported fasteners are used to mount the cover to the feed guide. This permits the cover portion to be readily removed for quick cleaning.
These and other features and advantages of the present invention will be apparent from the following detailed description, in conjunction with the appended claims.